The handheld scanner sweeps through the surface of the document by the hand movements of the user so as to obtain the contents of the document. Compared with the flatbed scanner, the handheld scanner can scan along a proper path without the limitation of the size of the original document and incorporate with the operation of combining images, so that the scanning operation of the large-sized document can be achieved.
However, when the handheld scanner is in use, it is difficult to move the scanner at a fixed speed. Moreover, during the period of scanning, the handheld scanner may deviate the predetermined scan path slightly or cause dither, and that results in distortion or deformation of the scanned image. Therefore, the handheld scanner is usually incorporated with a positioning module to detect the scan path for positioning the handheld scanner. Conventional handheld scanners utilize a single row or dual rows of rollers in combination with a rotary encoder or an optical mouse sensor to achieve the purpose of positioning the handheld scanner. While the roller is combined with rotary encoder for positioning, the scan path will be subject to the rolling restrictions and cannot change the scan direction arbitrarily. Alternatively, while the optical mouse sensor is used to sense the paper directly for positioning the handheld scanner, the scanner with the optical mouse sensor can change the moving direction to scan. However, the optical mouse sensor will easily produce errors due to the surface quality of different papers. Consequently, the handheld scanner with the optical mouse sensor cannot achieves to position precisely and it causes the image quality poor.
Therefore, there is a need of providing a positioning module and a handheld scanner using the same to overcome the above drawbacks.